Hi everyone, I am new to the cycling world (just got my first road bike this year) and have a stupid question to ask. I bought a used bike and it looks like the cassette, chain, and probably crankset are due to be replaced. The problem is that I don't know anything about sizing these things!

The cassette is a Shimano HG50, 12-25t; the chain is a Shimano HG73, 9-speed; and the crankset is an FSA Gossamer MegaExo, 2-piece crankset.

I assume that the chain length would depend on the number of teeth on the cassette and crankset, but I'm really lost with all of this so any guidance would be really appreciated!
Thanks!

It's a good idea to replace the cassette and chain. And possibly the bottom bracket. It's probably not likely that the chainrings on the crankset need replacing. For sizing the chain, I use Sheldon's Big-Big-Plus-One method.

See here.

Ah, ok. thanks very much! So if I understand correctly, I could pick up a new cassette and it doesn't matter if it is a 12-25t or 12-26t or 11-34t (or anything else, although I know this will affect the gearing) and then adjust the new chain to properly fit the new cassette.

As for the crankset, it looks like some of the teeth are chipped. Maybe I just need to replace the chainrings on it?

The crankset teeth aren't chipped. They're shaped like that on purpose to help with shifting. It's actually pretty genius how everything works.

Before you go replacing all sorts of potentially expensive parts, re-cable the bike. It may be that the cables are old and gunked up, and changing them would basically "fix everything that's currently wrong." Actually, you should do this anyway even if you do replace the cassette and chain.

Take a picture of what you are seeing as damage on your chainring and post it. Some chainrings have grooved sections on the teeth which help in shifting and things of that nature. If you're new to cycling you may be confusing these grooves for areas that are worn out and require replacement. Would hate for you to replace a perfectly good crank/chainrings.

edit: ^ Beat me to it.

Please note on the cassette size that your bike probable has a short cage derailleur and there will be a limit as to how big the largest cog can be.

as far as the cassette goes yes you can pick anything but you have a few limitaions. first would be that you need to buy a shimano or sram cassette because of the spacing between the cogs. second would be how low of a gear your RD will take. most short cage RD will handle a 28t but you would need a mid cage to go much lower. last you need to make sure it is the same speed as your current cassette (ie 9sp).

you can get any chain you want as long as it is a 9sp chain. others will work but 9sp is ideal. KMC makes a really good cheap 9sp chain the X9.93. i would suggest taking it to the bike shop to install both the chain and cassette if you have never done it before and ask them to show you how to do it the correct way.

as far as your chainrings go they should be fine. FSA does have some teeth that look "chipped" or not sharp on there large chainring so thats normal. if they are indeed broken off then yes replace them. you can ask the bike shop to inspect them when they install you cassette and chain. the only thing you need to look for there would be to get the right BCD. meaning 130mm for a standard crank or 110mm for a compact.

link to chain
https://bikeisland.com/cgi-bin/BKTK_S...ls&ProdID=1942

link to cassette
https://bikeisland.com/cgi-bin/BKTK_S...ils&ProdID=102

i knew by the time i typed that there would be 3 or 4 other answers saying close to the same thing. i also agree about the cables. thats a good way to make an old bike feel new.

Thank you all for being so helpful - I really appreciate it. I think I will definitely be best off to take the bike down to the local shop so I can take a look at everything with them and have them show me how to do some of these routine maintenance jobs.

After looking at some stock pics of the crankset/chainrings, it looks like those "chips" are supposed to be there (good thing I checked here before buying anything!).